Biological rhythms of organisms may be relative to light exposure. A conventional lighting system for an aquarium is operable to not emit light during the daytime and to emit light only after nightfall, for the purpose of better showcasing the aquarium. However, the time of lighting the aquarium is controlled by user operation, which may vary on a daily basis and cause disturbance of the biological rhythms of living creatures in the aquarium, and in turn adversely affect their growth